Why do people meditate?

Not everyone meditates for the same reason.  I know some people who meditate to feel more calm and peaceful.  I know others who meditate because they want to be more mindful and present to everyday life.  For me personally, I choose to meditate in order to wake up, to see reality as it truly is.  I meditate to become liberated and free from the grips of greed, aggression, and delusion.  Ultimately I meditate to know suffering and the freedom from suffering, thus becoming a benefit to myself and others.  As I said, everyone has their own reasons for meditating.  

Thanks for the question.  May much peace, ease, and wellbeing be with you :)

Meditation can be secular or spiritual.

Secular: health benefits including lowering blood pressure, decreasing axiety, increasing focus are a few well documented benefits.

Spiritual: destroying the ego, lifting the curtain of Maya, connecting with god(s) are some common themes

This is not an exhaustive list